Intelligent access control system

ABSTRACT

In operational environments where local loop generation equipment is used, communication interruptions between a central office and a customer premises device is minimized by using a dedicated communications link between the local loop generation equipment and the central office. A processing mechanism at the central office determines if, when, and under what circumstances the customer premises device will be notified in response to the activation of local loop generation equipment. This eliminates the need to place local loop generation equipment in series with a communications path that runs between the central office and the customer premises. The central office may provide the dedicated communications link in the form of a telephone line which is equipped to place outgoing local calls, but not equipped to receive incoming calls, and not equipped to place long-distance calls.

FIELD OF THE INVENTION

The present invention relates generally to telephonic communications,and, more particularly, to techniques for overcoming shortcomings oflocal loop generation equipment.

BACKGROUND OF THE INVENTION

Ever-increasing numbers of telephone customers may be coupled to localloop generation equipment, examples of which are security systems,doorbell answering devices, and access control mechanisms. Inparticular, doorbell answering systems are commonly utilized inmulti-family housing units. These systems generally place a switchingmechanism in series with the tip/ring lines running from the telephonecompany central switching office to the customer premises. Normally,this switching mechanism is closed, completing a circuit between theswitching office and the customer premises. In this closed state,customers are able to communicate voice and/or data over their telephonelines as if the access control system was not even present. However,this communication is subject to interruption at any time. When avisitor wishes to notify a person at a selected customer premises of hisor her presence, the visitor pushes a button, or presses one or morekeys on a keypad. The access control system responds to the button orkey presses by opening up the circuit between the customer and thecentral switching office, and by providing a local loop between thevisitor and the selected customer premises.

This open circuit is something of a nuisance if it interrupts a voicecall already in progress. However, the open circuit is also problematicin cases where the transfer of data is interrupted. For example, manypeople use a computer modem to access the Internet over conventionaltelephone lines. Once the circuit between the central office (CO) andthe computer modem is broken, the modem will disconnect from thetelephone line. The subscriber loses data during this interruption, andmay also be faced with the inconvenience of having to re-log into anonline service.

The circuit between the central office and the customer is broken sothat a local loop may be provided between the customer premises and anaccess door. After the circuit has been broken, the door answeringsystem then feeds a ringing signal to the telephone line serving thesubscriber's premises. When a person at the customer premises takes atelephone off-hook, voice communications are now enabled between thisperson and the visitor. If this person wishes to grant the visitoraccess, this person presses a specified DTMF tone sequence on thetelephone keypad or, alternatively, presses a lock release buttonseparate and apart from the telephone system to grant the visitoraccess.

Although the foregoing example deals with local loop generationequipment in the form of a doorbell answering system, other types oflocal loop generation equipment present similar problems. Whenever thelocal loop generation equipment creates a local loop, voice and datacommunications between the customer and the central office areinterrupted.

Refer to FIG. 1, which is a hardware block diagram of an illustrativeprior art access control system. This access control system placesintercom equipment 105 in series between central office 101 and housingunit 103. For the sake of clarity, FIG. 1 shows only one housing unit103, whereas, in a more typical application, intercom equipment 105would be placed in series between tip/ring wire pairs running from thecentral office 101 to each of a plurality of housing units. Tip/ringlines 115, 117 from central office 101 are coupled to a switchingmechanism 107 in intercom equipment 105. Switching mechanism 107selectively switches tip/ring lines 115, 117 to tip/ring lines 119, 121serving housing unit 103. Normally, switching mechanism 107 is closed,completing a circuit between the switching office and the customerpremises by coupling tip line 115 to tip line 119, and ring line 117 toring line 121. In this manner, customers are now able to place outgoingcalls, and also to receive incoming calls, as if the intercom equipment105 was not even present.

When a visitor wishes to notify a person at a selected housing unit 103of his or her presence, the visitor pushes a button, or presses one ormore keys on a keypad at a lobby interface device 111. In response tothe receipt of these keypress signals at switching mechanism 107,microprocessor 109 activates switching mechanism 107 to break theconnection between central office 101 and housing unit 103, and toconnect housing unit 103 to lobby interface device 111, thereby forminga local loop between lobby interface device 111 and housing unit 103.More specifically, switching mechanism 107 opens up the circuit betweentip line 115 and tip line 119, and also between ring line 117 and ringline 121, and closes the circuit between tip line 119 and tip line 123,as well as ring line 121 and ring line 125. The keypress signals aresent out over tip/ring lines 123, 125 which form the local loop betweenthe lobby interface device 111 and the switching mechanism 107. Thekeypress signals could, but need not, be DTMF signals or pulse dialingsignals.

The switching mechanism 107 forwards these keypress signals tomicroprocessor 109, which responds to the button or key presses byactivating switching mechanism 107. The intercom equipment 105 thenfeeds a ringing signal, via switching mechanism 107, to a telephone athousing unit 103. When a person at housing unit 103 takes the telephoneoff-hook, voice communications are now enabled between this person andthe visitor. If this person wishes to grant the visitor access, thisperson presses a specified DTMF tone sequence on the telephone keypador, alternatively, presses a lock release button separate and apart fromthe telephone system to grant the visitor access.

Unfortunately, whenever a visitor activates the lobby interface device111 to signal a resident, the resident may already be in data and/orvoice communication with central office 101. If, for example, theresident is communicating over the Internet, the Internet connectionwill typically be lost. These breaks in communication may occurunexpectedly, unpredictably, and repeatedly, causing the resident tobecome frustrated with the overall quality of telephone service.

SUMMARY OF THE INVENTION

In view of the foregoing deficiencies of the prior art, it is an objectof the invention to minimize the interruption of communications betweena central office and a customer premises when local loop generationequipment is in use.

It is a further object of the invention to intelligently control anyinterruption of communications over a telephone line between a centraloffice and one or more customer premises devices caused by theactivation of local loop generation equipment on this telephone line.

It is a still further object of the invention to allow a premisesoccupant to receive doorbell answering system telephone calls whilealready engaged in another telephone call.

It is a still further object of the invention to provide a premisesoccupant with a cancel door bell call waiting feature such that callwaiting tones will not be sent to the premises telephone when a visitoractivates the doorbell answering system and a call is already inprogress.

It is a still further object of the invention to provide a premisesoccupant with a call waiting feature such that only calls from thedoorbell answering system will cause call waiting tones to be sent tothe premises telephone.

In accordance with the objects of the invention, any interruption ofcommunications between a central office and a customer premises deviceis minimized by using a dedicated communications link between the localloop generation equipment and the central office. A processing mechanismat the central office determines if, when, and under what circumstancesthe customer premises device will be notified in response to theactivation of local loop generation equipment. This eliminates the needto place local loop generation equipment in series with a communicationspath that runs between the central office and the customer premises.

According to a further embodiment, the central office provides thededicated communications link in the form of a telephone line which isequipped to place outgoing local calls, but not equipped to receiveincoming calls, and not equipped to place long-distance calls.

According to a still further embodiment, the local loop generationequipment is a doorbell answering system, and the central office isadapted to implement advanced intelligent network (AIN) features. TheseAIN capabilities permit a premises occupant to receive doorbellanswering system telephone calls while already engaged in anothertelephone call. These AIN capabilities may also be employed to provide apremises occupant with a cancel door bell call waiting feature such thatcall waiting tones will not be sent to the premises telephone when avisitor activates the doorbell answering system and a call is already inprogress. Finally, these AIN capabilities may be used to provide apremises occupant with a call waiting feature such that only calls fromthe doorbell answering system will cause call waiting tones to be sentto the premises telephone.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other objects and advantages of the present inventionwill become apparent to those skilled in the art upon reading thefollowing detailed description of the preferred embodiments inconjunction with a review of the appended drawings in which:

FIG. 1 is an electrical block diagram showing typical prior artinterconnections between customers and a central office in anoperational environment where local loop generation equipment isemployed.

FIG. 2 is an electrical block diagram of a system equipped to provideminimal interruption of communications between a central office and acustomer in an operational environment where local loop generationequipment is used.

FIG. 3 is a more detailed electrical block diagram of the lobbyinterface device, intercom equipment, and access control device shown inFIG. 2

FIGS. 4A–4D together comprise a flowchart setting forth a firstillustrative operational sequence performed by the configuration of FIG.3.

FIG. 5 is a flowchart setting forth a second illustrative operationalsequence performed by the configuration of FIG. 3.

FIG. 6 is a hardware block diagram of a system equipped to provideminimal interruption of communications between a central office and acustomer in an operational environment where the central office utilizesadvanced intelligent network (AIN) protocols.

FIGS. 7A and 7B together comprise a flowchart setting forth anillustrative operational sequence performed by the configuration of FIG.6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Refer to FIG. 2 which is an electrical block diagram of a systemequipped to provide minimal interruption of communications between acentral office and a customer in an operational environment where localloop generation equipment is used. One fundamental distinction betweenthe system of FIG. 2 and the prior art configuration of FIG. 1 is thatthe system of FIG. 2 does not place intercom equipment 205 in seriesbetween central office 101 and housing unit 103. Considering FIG. 2 ingreater detail, note that only one housing unit 103 is shown. This isfor purposes of illustration only as, in a more typical application,intercom equipment 105 would provide service to a plurality of housingunits 103 served by central office 101. Such housing units 103 may, butneed not, represent individual apartments, townhouses, condominiums,offices, and/or single family homes which are organized into a largercomplex, subdivision, campus, and/or planned unit development. As shown,tip/ring lines 120, 122 run between central office 101 and housing unit103. Tip/ring lines 124, 126 from central office 101 are coupled to atelephone line interface 207 in intercom equipment 105. Telephone lineinterface 207 also provides a mechanism for selectively switchingrespective tip and ring lines 124, 126 to corresponding tip and ringlines 128, 130 serving a lobby interface device 111. This switchingmechanism is controlled by a microprocessor 209, operating inconjunction with a memory 211. One or more I/O devices 213 may beutilized to program the microprocessor, to provide commands to themicroprocessor, and/or to accept output signals from the microprocessor.The microprocessor 209 also controls the operation of an access controldevice 113. Examples of access control devices are electronic doorlocks, solenoid-controlled latches, other types of latching mechanisms,and other programmable-controlled locking and/or enabling mechanisms.

In the configuration of FIG. 2, note that the capability of providing acommunications pathway between central office 101 and housing unit 103exists at all times. This pathway, formed over tip/ring lines 120, 122,exists irrespective of the status of intercom equipment 105. In thismanner, digital and/or voice communication between the central office101 and the housing unit 103 are not subject to being directlyinterrupted by intercom equipment 205. Communications on tip/ring lines120, 122 are under the control of central office 101.

When a visitor wishes to notify a person at a selected housing unit 103of his or her presence, the visitor pushes a button, or presses one ormore keys on a keypad at a lobby interface device 111. In response tothe receipt of these keypress signals at telephone line interface 207,microprocessor 209 activates telephone line interface 207 to place anoutgoing telephone call to central office 101. The microprocessor 209controls telephone line interface 207 such that the outgoing callincludes data uniquely identifying the housing unit 103 for which thevisitor wishes to signal his or her presence. This data may, but neednot, be specified in the form of a standard DNI (dialed numberidentifier). Unlike the prior art system of FIG. 1, the connectionbetween the central office 101 and the housing unit 103 is notautomatically broken when the visitor activates the lobby interfacedevice 111. Moreover, the system of FIG. 2 does not create a local loopbetween lobby interface device 111 and housing unit 103.

The outgoing call placed by intercom equipment 205 is received atcentral office 101. A processing mechanism at the central office 101uses data associated with this call, such as, for example, the DNI data,to determine what, if any, further action should be taken. Thisprocessing mechanism may, but need not, make this determination byreferring to a lookup table stored in a memory device at the centraloffice 101. For example, the DNI may be used to place a call to thehousing unit 103 specified by the visitor. Certain DNIs may correspondto housing units 103 which do not wish to be disturbed, whereupon thecentral office 101 will not place a call to the housing unit specifiedby the visitor, but will instead transmit a prompt message to intercomequipment 205, indicating that this housing unit cannot be signaled fromintercom equipment 205. When the central office 101 places a call to agiven housing unit 103 in response to a visitor signaling the housingunit from intercom equipment 205, the call may be answered by anoccupant at housing unit 103.

Pursuant to a further embodiment of the invention, microprocessor 209 ofintercom equipment 205 may be programmed so as to signal to centraloffice 101 the housing unit identification only in the form of an“encoded” dialed number. At the central office 101, AIN capabilities canbe utilized to convert the “encoded” housing unit identifier, i.e., thedialed number, into the housing unit's actual phone number. Each ofthese “encoded” numbers could, but need not, represent a uniquecombination of DTMF digits that is assigned to a given housing unit.Accordingly, the AIN capabilities are used to map the sequence of DTMFdigits entered into intercom equipment 205 by a visitor into an actualtelephone number. Since the actual phone numbers of the housing unitsare resident in an AIN-equipped central office 101 database, and notprovided to visitors, this option provides additional security forhousing unit residents. This option also preserves the secrecy ofunlisted telephone numbers.

If the call is answered, the central office 101 provides a voicecommunications path between housing unit 103 and intercom equipment 205so that the visitor can talk with the occupant at housing unit 103. Ifthe occupant wishes to grant the visitor access, the occupant presses aspecified DTMF tone sequence on his or her telephone keypad or,alternatively, presses a lock release button separate and apart from thetelephone system to grant the visitor access. In cases where theoccupant enters a DTMF sequence, the sequence is received at centraloffice 101 and then conveyed to intercom equipment 205. The telephoneline interface 207 receives the DTMF sequence, and the microprocessorcompares the entered sequence to a sequence stored in memory 211 andcorresponding to the occupant's housing unit 103. If the comparisonindicates matching DTMF sequences, then the microprocessor 209 causesaccess control device 113 to grant the visitor access.

Optionally, the central office 101 processing mechanism may beprogrammed to place a call to a given housing unit 103 only in theabsence and/or presence of certain types of communications on tip/ringlines 120, 122. For example, a subscriber at a given housing unit 103may not wish to be disturbed by a visitor if he is on the Internet, butif the subscriber is engaged in a voice call, he would like to benotified of the existence of the visitor. For each of a plurality ofhousing units 103, the aforementioned lookup table may be equipped withfields specifying what types of communications on tip/ring lines 120,122 should, or should not, be interrupted.

The central office 101 may also offer an optional feature whereby, inresponse to a visitor signaling a given housing unit 103 on intercomequipment 205, the central office will place an outgoing call to thathousing unit using call waiting and/or identa-ring (distinctive ringing)features. This feature may also be implemented using a look-up tableindicative of whether each of a plurality of housing units 103subscribes to one or more of the aforementioned features.

FIG. 3 is a more detailed electrical block diagram of the lobbyinterface device, intercom equipment, and access control device shown inFIG. 2. Note that intercom equipment 205, lobby interface device 111,and access control device 113 are shown as discrete elements in FIG. 2for purposes of illustration, it being clearly understood that one ormore of these elements may be combined. The configuration of FIG. 3encompasses implementations where discrete elements are employed, aswell as other implementations where various elements may be integratedtogether. Also, the microprocessor 209 of FIG. 2 is also shown forillustrative purposes, it being understood that virtually any processingmechanism could be employed. Whereas the system of FIG. 2 utilized aprocessing mechanism in the form of microprocessor 209, the system ofFIG. 3 sets forth an embodiment which implements this processingmechanism using a central processing unit (CPU) 309.

CPU 309 is coupled to non-volatile memory 311 over a bus 310. Bus 310 isused to connect each of a plurality of peripherals to the CPU 309.However, many peripherals to the CPU 309 may alternatively be connectedvia dedicated ports on the CPU. As a general matter, devices thatrequire very high throughput are connected to the CPU 309 via bus 310.Such devices include data storage drives and memory. An optionalslow-scan video system 320 may also be coupled to bus 310.

Non-volatile memory 311 includes program memory 312 as well as datamemory 314. Data memory 314 is used to store information required by anaccess control program executed by CPU 309. One example of thisinformation includes a database of telephone numbers (FIG. 4, 426) thatstores phone number(s) to be dialed by DTMF codec 326 (to be describedin greater detail below) when a user at console terminal 315 wishes tosignal their presence to a housing unit occupant. Each of these phonenumbers is associated with a corresponding code identifier which aconsole user enters into a console keypad 313 so as to initiate a callto a selected housing unit 103. Data memory 314 is non-volatile, andshould be equipped so as to accept updates of information from CPU 309.

A console keypad 313 is coupled to CPU 309, and may, but need not,include an array of switches or buttons. Console keypad 313 could alsobe implemented using a conventional QWERTY computer keyboard. The onlyrequirement for console keypad 313 is that it provide some mechanism bywhich a visitor can select and signal a given housing unit. A consoleterminal 315 is also coupled to CPU 309. Illustrative implementations ofconsole terminal 315 include some type of display device (CRT(cathode-ray tube) monitors, LCD display screens, LED display panels,and/or other mechanisms for indicating and/or displaying information)combined with an input mechanism such as a conventional QWERTY computerkeyboard. Console terminal 315 is used to configure the system of FIG. 3as, for example, by establishing and maintaining one or more datatables. These data tables associate key and/or button presses on theconsole keypad 313 with housing unit telephone numbers. The interfacealso allows access to other CPU 309 programmable options such astime-out values for call progress and mute functions. The consoleterminal 315 can also be used to import new versions of CPU 309 softwareand changes to PCM decoder 328 prompts. In addition, the consoleterminal can be used to output diagnostic information such as a requestfor maintenance.

Microphone 330 is a transducer that accepts acoustical energy input as,for example, from a visitor, and converts this energy into electricalsignals. Microphone 330 can be implemented using a microphone of thetype employed on telephone handsets. Moreover, if privacy is desired, atelephone handset can be used in lieu of, or in addition to, speaker 334and microphone 330.

Speaker 334 is a transducer that accepts electrical input signals andconverts them into acoustical energy. Speaker 334 can be implementedusing a transducer of the type employed in the earpiece of a telephonehandset, and/or a speaker of the type found in radios and various othertypes of electronic devices. Also, the console terminal 315 may employanother speaker for the output of the PCM decoder 328 to ensure that thePCM output is audible at all times. Another illustrative configurationis to have both a speaker and a handset in a cradle. When the handset isremoved from its cradle, i.e., placed off-hook, the speaker would thenbe muted.

For security reasons, it may be desirable to prevent visitors fromintroducing (by way of microphone 330) and from monitoring (by way ofspeaker 334) any DTMF tones that may occur on the telephone connectionto the central office. Provision of a security mechanism is generallydesirable for the following reasons. (1) The housing unit telephonenumber may be unlisted. If the DTMF tones are audible on the speakerwhen the console dials the number, a visitor could record and decodethis DTMF to reveal the number. (2) The visitor could transmit asequence of DTMF tones in an attempt to command lock release 324 to openthe door latching mechanism. (3) The visitor may attempt to use a DTMFtone generator to place long-distance or toll calls over microphone 330.In the configuration of FIG. 3, a security mechanism is provided in theform of DTMF filter 332, which acts as a filter for microphone 330, andDTMF filter 338/muting device 336, which acts as a filter for speaker334.

Muting device 336, under the control of CPU 309, is used to activate anddeactivate the speaker 334. This device can be used in addition to DTMFfilter 338, and/or instead of DTMF filter 338, for securing information.For instance, when the DTMF codec 326 starts dialing a housing unittelephone number, the muting device 336 will disconnect the speaker 334so that the visitor cannot hear the DTMF signals being sent to thecentral office 101 (FIG. 1). In the case of the door lock releasesignal, the CPU 309 could be programmed to activate muting device 336whenever the muting device detects a DTMF tone, and to deactivate themuting device when a specific DTMF tone is detected, and/or at the endof a specified time period. When the muting device 336 is activated,this means that it attenuates audio signals sent to speaker 334 suchthat the signals do not generate substantially audible acousticalenergy. When the muting device 336 is deactivated, it passes audiosignals, substantially unattenuated, from DTMF filter 338 to speaker334. For example, in actual operation, assume that the door lock releasecode is a multiple digit DTMF code. The muting device 336 clips thefirst DTMF tone as the device enters the activated state, and subsequentDTMF digits are inaudible. The muting device 336 becomes deactivatedupon reception of the final DTMF digit of the door lock release code, orif the connection between the housing unit 103 (FIG. 1) and the DTMFcodec 326 were lost after a timeout of a programmable duration.

If the door lock release signal was, for instance, 6736# (note that 6736spells out the word OPEN on a telephone keypad), the visitor might heara very brief portion of a DTMF “6” tone, then the speaker 334 would bemuted. After reception of the # signal, the muting device 336 would bedeactivated. The use of a multiple digit DTMF door lock release code hassecurity advantages. A multi-digit code renders hacking much moredifficult than if a single-digit code were to be employed. Also, therelease code is programmable such that, in the event of a successfulhacking attempt, the system proprietor can re-program and re-secure thesystem.

Pulse code modulation (PCM) decoder 328 provides a mechanism forgenerating audio signals in response to information received from theCPU 309. These audio signals may, but need not, include voice prompts,tones, tone sequences, beeps, and simple melodies. For example, the PCMdecoder 328 could be used to output a digitally stored message such as“You may now enter” that is played when a housing unit occupant signalsthe console to allow the visitor to enter. The PCM decoder 328 couldalso be used to generate tones, beeps, and/or simple melodies, toindicate positive feedback when keys are depressed, and to indicate thatthe door latching mechanism is released. Illustrative conditions forwhich PCM decoder 328 is used to provide audio signals are as follows:(1) so as to provide positive audio feedback when a user presses a keyon console terminal 315 and/or console keypad 313; (2) to providemessages to a visitor at console keypad 313 indicating current systemstatus, such as “please wait”, “we are contacting the occupant of thehousing unit now”; “you may now enter”; and “for deliveries, pleasecontact the Superintendent”. Many of these prompts may be activated bycall progress detection logic in telephone interface 340. For instance,a “busy” signal is indicative that a housing unit occupant does not wishto be disturbed, and would trigger the playback of an appropriate voicemessage.

CPU 309 controls the operation of a lock release mechanism 324, a DTMFcoder-decoder (codec) 326, and an access device reader 322. The DTMFcodec 326 is used to initiate phone calls and to decipher touch tonessent by the housing unit occupant to the intercom equipment 205 (FIG.2). The lock release 324 can be implemented, for example, using a drycontact switch. The state of the contacts of this switch (open orclosed) is under the control of the CPU 309. In typical systemapplications, house current is used as a power source, such that thecontacts should be equipped to handle voltages up to at least 120 VAC.However, it is alternatively possible to use other power sources,whereupon appropriate contact ratings should be employed. In many systemapplications, the contacts are normally open, and are placed in theclosed state when the door latch is released.

The access device reader 322 may be implemented using any of a varietyof devices including, for example, a smart card reader, a magnetic cardswipe reader, a bar code reader, a simple contact closure, a data inputdevice, a proximity card reader, and/or an RF transponder. An example ofa simple contact closure would be a key-operated switch. A key isinserted into a tumbler and, when turned, closes a set of contacts thatsends an interrupt signal to the CPU 309. In response to this interruptsignal, the CPU 309 is programmed to activate the door lock release 324to permit the door to be opened.

A more sophisticated implementation of access device reader 322 involvesa reader device such as a magnetic card reader or a transponderreceiver. In this implementation, data from the reader device is sent toCPU 309 which verifies the data against a verification database storedin data memory 314 and releases the door lock release 324 mechanism ifthe data from the reader device is valid.

Slow-scan video system 320 provides a mechanism for sending videoinformation acquired by a camera in the vicinity of an access door to aremote location. This remote location can be a housing unit 103 and/orother security checkpoint. In the case of a housing unit 103, theoccupant would most likely be equipped with a video-capable modem.Alternatively, dedicated coaxial cable lines could be provided from thecamera to one or more housing units. In the case of a video-capablemodem, the DTMF codec 326 and telephone interface 340 could be combinedinto a modem device that supports simultaneous voice and data. Thiswould allow slow scan video to move over a conventional tip-ringtelephone line for decoding and display in the housing unit 103. Theslow-scan video system 320 may, but need not, be equipped to capture oneor more digital images. Having slow scan digital image capturecapability could be particularly useful if combined with one-button 911dialing. Depressing the 911 emergency key could be used to trigger thecapture of image data that would assist law enforcement personnel.

Telephone interface 340 provides FCC (Federal Communications Commission)compliance to Part 95 and Part 86 of FCC Rules and Regulations.Interface 340 also provides call progress functions and monitoring.Illustrative call progress functions are on-hook, off-hook, ring detect,dial tone detect, busy detect, and call completion. Telephone interface340 may also provide one or more standard RJ-11 jack connections.

Before power is first applied to the system of FIG. 3, or when power toone or more devices of FIG. 3 is restored after a power failure, thedevices shown in FIG. 3 should be placed in the following states as partof an initialization process. The telephone interface 340 should be inthe on-hook state, and the lock release 324 should be “open”. In thiscontext, “open” means that the circuit to the lock release 324 mechanismis incomplete and, therefore, the lock is not released, but remains inthe locked position. Upon application of power, the CPU 309 initializesother devices as follows. The CPU 309 first loads a copy of theoperating system from program memory 312, along with current copies of aconsole terminal interface program and an application program. The CPU309 downloads a button/telephone table from data memory 314, and alsodownloads program parameters such as time-outs. Variable space in datamemory 314 is initialized to zero. The lock release 324 is open-circuit(locked—door secure), and the DTMF codec 326 is set to decode incomingDTMF signals. The console keypad 313 is “read”, the PCM decoder 328 isset to “silent”, the microphone 330 is “read”, the speaker 334 is set to“silent”, the muting device 336 is turned off, and the telephoneinterface 340 is set on-hook.

The CPU 309 automatically starts the current version of the applicationsoftware at the time of startup. At about the same time, a process toprovide a supervisory interface is started and attached to the consoleterminal 315 interface. The process could either use a multi-taskingoperating system or a simple foreground/background program. As part ofthe application startup, the program should access telephone interface340 and place it in the off-hook condition so as to wait for detectionof dial tone. If, after an appropriate time period, no dial tone isdetected, the CPU 309 uses the PCM decoder 328 to output an appropriateerror message to speaker 334. If this is the first time that the systemof FIG. 3 has been used, then the supervisory interface program will berequired to accept input parameters and table values that map consolekeypad 313 buttons to appropriate telephone numbers.

When a visitor wishes to call an occupant of a housing unit 103 (FIG.2), they approach console keypad 313 and examine labels next to thekeypad 313 to identify and depress one or more buttons corresponding tothe housing unit they wish to contact. These depressed buttons are readby the application program running on CPU 309 (FIG. 3). The value(s)read by the CPU 309 are then used as key value(s) for indexing a lookuptable of telephone numbers. If the table entry corresponding to the readkey value(s) is empty, then an appropriate PCM-encoded message isoutputted to the speaker 334 (i.e., “this tenant does not acceptvisitors”). If there is a phone number associated with the read keyvalue(s), then the steps outlined in FIGS. 4A–4D are performed.

FIGS. 4A–4D together comprise a flowchart setting forth an illustrativeoperational sequence performed by the configuration of FIG. 3. Theprogram commences at block 401 where a visitor presses one or more keyson console keypad 313 (FIG. 3) to notify a selected occupant premises(i.e., a housing unit 103) of the visitor's presence. At block 403, theCPU 309 searches the lookup table of telephone numbers to retrieve adatabase entry corresponding to the key or keys pressed by the visitor.Does the CPU retrieve a database entry? If not, the program goes toblock 407 where the CPU triggers the outputting of an error message toPCM decoder 328 and speaker 334 (FIG. 3). The program then loops back toblock 401.

The affirmative branch from block 403 leads to block 405 where the CPUsignals DTMF codec 326 (FIG. 3) to dial the telephone number specifiedby the lookup table of telephone numbers. At block 409, the DTMF codecplaces a telephone call over a dedicated answering service telephoneline (tip line 124 and ring line 126 of FIG. 2) to the central switchingoffice 101 (FIG. 2). The central office receives the call from the DTMFcodec and uses the DNI (dialed number identifier) of the received callto place an outgoing call to the occupant premises (i.e., housing unit103 of FIG. 2), optionally using call waiting and/or identa-ring(distinctive ringing) features (FIG. 4B, block 411). At block 413, anindividual at the occupant premises answers the call placed by thecentral office and can communicate with the visitor via the speaker 334(FIG. 3) and/or microphone 330 (FIG. 3).

An individual at the occupant premises may, if desired, grant thevisitor access (block 415) by pressing a predetermined DTMF key or keyson the telephone device used to answer the call at block 413. However,note that an alternate or additional mechanism for access control may beprovided in the form of a separate signalling facility as, for example,a pair of wires used to close a contact, thereby releasing the doorlock. This separate signalling facility is shown in FIG. 3 as a “grantaccess” signal input device 342 that is coupled to CPU 309. The DTMFcodec receives the DTMF tone(s) entered at block 415 and forwards thedecoded tone(s) to the CPU (block 417). The CPU compares the decodedtone(s) with access code(s) stored in non-volatile memory (block 419).Do the coded tones match any access code(s) stored in memory? If not,the program advances to block 424 where the CPU and the codec send anerror message to the telephone device used to answer the call at block413. The program then loops back to block 415.

The affirmative branch from block 419 leads to block 421 where the CPUactivates the lock release mechanism, thereby providing the visitor withaccess. The CPU then instructs the codec to place the telephoneinterface on-hook (block 423) and the operational sequence of FIGS.4A–4D terminates.

FIG. 5 is a flowchart setting forth a second illustrative operationalsequence performed by the configuration of FIG. 3. The operationalsequence commences at block 501 where CPU 309 (FIG. 3) is in an idlestate until a button on console keypad 313 (FIG. 3) is pressed (FIG. 5,block 503). Once the button is pressed, at block 505, the CPU activatesthe muting device (FIG. 3, 336). The telephone interface (FIG. 3, 340)is placed in an off-hook state (block 507), and the telephone interfacethen waits for a dial tone to be detected (block 509). If dial tone isnot detected within a specified time-out period (block 511), the PCMdecoder 328 (FIG. 3) outputs an error message (block 527), the telephoneinterface is placed in an on-hook state (block 529) and the programloops back to block 501.

If dial tone is detected within the time-out period (block 511), theprogram advances to block 513 where the DTMF codec (FIG. 3, 326) dialsthe number associated with the button(s) pressed at block 503. The CPUinstructs the codec to dial the appropriate number by referring to adatabase of telephone numbers stored in memory (block 526). The mutingdevice is then deactivated, allowing audio to pass through (block 515).The telephone interface counts ring detects (block 517), and performs atest to ascertain whether or not a specified maximum number of ringcounts have been exceeded (block 519). If the maximum number of ringcounts have been exceeded, the program advances to block 525 where thePCM decoder plays out a message “No one is answering the telephone”, andthe program then loops back to block 529. If the maximum number of ringcounts has not been exceeded, the program advances to block 521 wherethe call is answered by someone at the occupant premises. A call timeris started to time the duration of the answered call. If the timeduration of the answered call exceeds a specified duration, the programloops back to block 529.

FIG. 6 is a hardware block diagram of a system equipped to provideminimal interruption of communications between a central office and acustomer in an operational environment where the central office utilizesadvanced intelligent network (AIN) protocols. Conceptually, thisillustrative embodiment utilizes local loop generation equipment in theform of a doorbell answering system. This embodiment uses AINcapabilities so as to allow a premises occupant to receive doorbellanswering system telephone calls while already engaged in anothertelephone call. These AIN capabilities may also be employed to provide apremises occupant with a cancel door bell call waiting feature such thatcall waiting tones will not be sent to the premises telephone when avisitor activates the doorbell answering system and a call is already inprogress. Finally, these AIN capabilities may be used to provide apremises occupant with a call waiting feature such that only calls fromthe doorbell answering system will cause call waiting tones to be sentto the premises telephone.

Pursuant to the aforementioned AIN capabilities, central office 101(FIG. 6) is equipped with an AIN (advanced intelligent network) servicessignaling point (SSP) 610. In practice, the SSP 610 may be implementedusing AIN software executed by a processing mechanism at the centraloffice 101. An example of suitable AIN software is developed on a systemgenerally known as the Integrated Service Control Point (ISCP)™. The SSP610 is coupled to one or more signaling transfer points (STP) 620 and aservice control point (SCP) 640. The STP 620 and/or the SCP 640 may, butneed not, be part of telephone network 630. The STP 620 forwards queriesfrom the central office SSP 610 to the service control point (SCP) 640.Although FIG. 6 shows one signaling transfer point (STP) 620, this isfor convenience, as any number of STPs 620 may be present. The signalingtransfer point(s) (STP) 620 are also utilized for the purpose oftransferring response messages from the service control point (SCP) 640to the central office 101. Examples of queries include requests for calloriginator identity and requests for called number identity. Thesequeries may also include standard OHD-type messages of the typewell-known to those skilled in the art. Response messages instruct theSSP 610 at the central office 101 to take a certain action as, forexample, to route the call to a telephone number based upon the receiptof a query message from the SSP 610.

In the context of the aforementioned AIN embodiment, an illustrativeoperational sequence may proceed as follows. First, a customer (thevisitor) dials into the central office and accesses the AIN SSP. The SSPthen queries the SCP with a standard TCAP message of the type well-knownto those skilled in the art. The SCP performs logic to determine if theresidence specified by the customer in the standard TCAP message wantsto receive a ringing signal when a visitor activates the doorbellanswering system and, if so, what type of ringing signal (i.e.,distinctive ringing) is to be provided. The SCP responds back to the SSPwith instructions to route the call to a number corresponding to theresidence specified by the customer and ring the residence phone with adistinctive ringing signal. Finally, the call is routed to the residencewith the distinctive ringing signal. The AIN SSP monitors the durationof the call (if answered), and disconnects the call after a specifiedduration of, say, 120 seconds. A more specific operational sequence ispresented in FIGS. 7A and 7B.

FIGS. 7A and 7B together comprise a flowchart setting forth anillustrative operational sequence performed by the configuration of FIG.6. The sequence commences at block 701. At block 703, the visitorpresses a doorbell button provided by the doorbell answering system(DAS) (FIG. 6, 605) console. The doorbell answering system CPU (FIG. 3,309) looks up the telephone number of the tenant corresponding to thebutton pressed and dials a predefined telephone number (block 705) overtip/ring lines 124, 126 (FIG. 2). Next (block 707), the AIN-equippedcentral office 101 (FIG. 6) assigns an OHD trigger against the doorbellanswering system line that includes tip/ring lines 124, 126 (FIG. 2).The SCP 640 (FIG. 6) identifies the dialed number as a tenant andinstructs the SSP 610 (FIG. 6) to route the call to the tenant'stelephone line (tip/ring lines 120, 122 of FIG. 2), and optionally toapply distinctive ringing to that call.

A test is implemented at block 709 to ascertain whether or not thetenant subscribes to call waiting. If not, the program advances to block711 where the tenant's line should be provisioned with selective callwaiting, generally known to those skilled in the art as the “CLASS”feature. In this manner, only calls from the doorbell answering systemwill initiate the call waiting function. Alternatively, a T_(—)Busytrigger could be assigned to all tenants. The SCP 640 (FIG. 6) wouldthen determine if the central office should offer a call to the tenant'stelephone line based on caller ID. If an incoming call is not from thedoorbell answering system, the SCP would route the call to busytreatment or forward the call to a network-based voice mail system, forexample. The program then advances to block 713.

The operations of block 713 are performed if the affirmative branch fromblock 709 is followed or, alternatively, after the operations of block711 have been performed. At block 713, the central office processesincoming calls from the doorbell answering system as it would any otherincoming call, except that the AIN controlling leg treatment from thedoorbell answering system OHD trigger, as well as subsequent routinginstructions, are used to provide distinctive ringing and/or callwaiting (CW) tones on the tenant's line. This distinctive ringing and/orCW tones are used to indicate that an incoming call to the tenant isfrom the doorbell answering system. Central office switch-basedselective CW or T_(—)Busy triggers are applied to calls from thedoorbell answering system to tenants that do not already subscribe tocall waiting. However, if the tenant has enabled call blocking, thecentral office honors this enablement, and a Busy signal is returned tothe doorbell answering system over tip/ring lines 124, 126 (FIG. 2).

At block 715, a caller ID—calling name identification is sent to theaccess door controlled by the doorbell answering system. The tenantanswers the call (block 717) and is connected to the doorbell answeringsystem's speaker 334 and/or microphone 330 (FIG. 3). The doorbellanswering system filters out any DTMF tones introduced by the visitorthrough the microphone input (as discussed previously in conjunctionwith FIG. 3).

At blocks 721 and 725, the tenant indicates whether or not he wishes toadmit the visitor (caller) by pressing a predefined DTMF key. If thetenant does not wish to admit the visitor, the call is disconnected(block 723). If the tenant does wish to admit the caller, the programadvances to block 727 where the doorbell answering system awaits thearrival of an “open door” DTMF tone sequence. Once the sequence isreceived (block 729), DTMF filter 338 (FIG. 3) filters out the DTMF“open door” sequence so that it is not audible to the visitor. Thedoorbell answering system then activates the lock release 324 (FIG. 3)for a fixed time and indicates to the visitor that he or she can enter.The

1. An apparatus for minimizing interruption of communications on a firstcommunications link between a central office and a customer premisestelephonic device in response to activation of local loop generationequipment, the apparatus comprising: (a) a second communications linkbetween the local loop generation equipment and the central office; (b)a processing mechanism at the central office coupled to the secondcommunications link and adapted to determine under what circumstancesthe customer premises telephonic device will be notified over the firstcommunications link in response to the activation of local loopgeneration equipment.
 2. The apparatus of claim 1 wherein the secondcommunications link is provided in the form of a telephone line which isequipped to place outgoing local calls, but not equipped to receiveincoming calls, and not equipped to place long-distance calls.
 3. Theapparatus of claim 1 wherein the local loop generation equipment is adoorbell answering system.
 4. The apparatus of claim 1 wherein thecentral office utilizes advanced intelligent network (AIN) protocolsadapted to permit a premises occupant to receive doorbell answeringsystem telephone calls on the first communications link while alreadyengaged in another telephone call on the first communication link. 5.The apparatus of claim 4 wherein the AIN capabilities are adapted toprovide a premises occupant with a cancel door bell call waiting featuresuch that the central office will not send call waiting tones on thefirst communications link when a visitor activates the doorbellanswering system and a call is already in progress.
 6. The apparatus ofclaim 4 wherein the AIN capabilities are used to provide a premisesoccupant with a call waiting feature such that only calls from thedoorbell answering system will cause call waiting tones to be sent onthe first communications link.
 7. An apparatus for intelligentlycontrolling any interruption of communications over a first telephoneline between a central office and one or more customer premises devicescaused by the activation of local loop generation equipment on the firsttelephone line the apparatus comprising: (a) a second telephone linebetween the local loop generation equipment and the central office; (b)a processing mechanism at the central office coupled to the secondtelephone line and adapted to determine under what circumstances thecustomer premises telephonic device will be notified over the firsttelephone line in response to the activation of local loop generationequipment.
 8. The apparatus of claim 7 wherein the second telephone lineis equipped to place outgoing local calls, but not equipped to receiveincoming calls, and not equipped to place long-distance calls.
 9. Theapparatus of claim 7 wherein the local loop generation equipment is adoorbell answering system.
 10. The apparatus of claim 7 wherein thecentral office utilizes advanced intelligent network (AIN) protocolsadapted to permit a premises occupant to receive doorbell answeringsystem telephone calls on the first telephone line while already engagedin another telephone call on the first telephone line.
 11. The apparatusof claim 10 wherein the AIN capabilities are adapted to provide apremises occupant with a cancel door bell call waiting feature such thatcall waiting tones will not be sent on the first telephone line when avisitor activates the doorbell answering system and a call is already inprogress.
 12. The apparatus of claim 10 wherein the AIN capabilities areused to provide a premises occupant with a call waiting feature suchthat only calls from the doorbell answering system will cause callwaiting tones to be sent on the first telephone line.
 13. An apparatusfor allowing a premises occupant to receive an incoming telephone callplaced from a doorbell answering system on a first telephone line whilethe first telephone line is already in communication with a centraloffice and the premises occupant is engaged in a telephone call on thefirst telephone line, the apparatus comprising: (a) a second telephoneline between the doorbell answering system and the central office; (b) aprocessing mechanism at the central office coupled to the secondtelephone line and adapted to determine under what circumstances thecustomer premises occupant will be notified over the first telephoneline in response to the activation of the doorbell answering system. 14.The apparatus of claim 13 wherein the processing mechanism furthercomprises a mechanism for providing the customer premises occupant witha door bell call waiting feature such that the central office will sendcall waiting tones over the first telephone line when a visitoractivates the doorbell answering system and the customer premisesoccupant is already engaged in a telephone call on the first telephoneline.
 15. The apparatus of claim 13 wherein the processing mechanismfurther comprises a mechanism for providing the customer premisesoccupant with a cancel door bell call waiting feature such that thecentral office will not send call waiting tones over the first telephoneline when a visitor activates the doorbell answering system and thecustomer premises occupant is already engaged in a telephone call on thefirst telephone line.
 16. The apparatus of claim 13 wherein theprocessing mechanism further comprises a mechanism for providing thecustomer premises occupant with a door bell call waiting feature suchthat the central office will send call waiting tones over the firsttelephone line only when a visitor activates the doorbell answeringsystem and the customer premises occupant is already engaged in atelephone call on the first telephone line.
 17. The apparatus of claim13 wherein the second telephone line is equipped to place outgoing localcalls, but not equipped to receive incoming calls, and not equipped toplace long-distance calls.
 18. A method for minimizing interruption ofcommunications on a first communications link between a central officeand a customer premises telephonic device in response to activation oflocal loop generation equipment, the method comprising the steps of: (a)providing a second communications link between the local loop generationequipment and the central office; (b) utilizing a processing mechanismat the central office, coupled to the second communications link, fordetermining under what circumstances the customer premises telephonicdevice will be notified over the first communications link in responseto the activation of local loop generation equipment.
 19. A method forintelligently controlling any interruption of communications over afirst telephone line between a central office and one or more customerpremises devices caused by the activation of local loop generationequipment on the first telephone line, the method comprising the stepsof: (a) providing a second telephone line between the local loopgeneration equipment and the central office; (b) utilizing a processingmechanism at the central office, coupled to the second telephone line,for determining under what circumstances the customer premisestelephonic device will be notified over the first telephone line inresponse to the activation of local loop generation equipment.
 20. Amethod for allowing a premises occupant to receive an incoming telephonecall placed from a doorbell answering system on a first telephone linewhile the first telephone line is already in communication with acentral office and the premises occupant is engaged in a telephone callon the first telephone line, the method comprising the steps of: (a)providing a second telephone line between the doorbell answering systemand the central office; (b) providing a processing mechanism at thecentral office, coupled to the second telephone line, for determiningunder what circumstances the customer premises occupant will be notifiedover the first telephone line in response to the activation of thedoorbell answering system.
 21. A method for controlling visitor accessto an occupant premises, the method comprising the steps of: (a) using aphone dialing mechanism to place a telephone call; (b) the telephonecall causing a notification to be provided from a central office to atelephonic device at the occupant premises, the notification signifyingthat a visitor is present; (c) an automated voice enunciation mechanismproviding an enunciated voice message to the visitor indicative ofprogress of the telephone call and corresponding to at least one of busysignal, dial tone, and an answered call; d) when the telephone call isanswered, providing a communications path between the visitor and theoccupant premises so as to enable an occupant to determine whether ornot to grant access to the visitor; and e) activating an access controlmechanism at the occupant premises if access is to be provided to thevisitor.
 22. The method of claim 21 wherein the communications path isprovided using a slow scan video link.
 23. The method of claim 22wherein the slow scan video link is implemented using modems.
 24. Asystem for controlling visitor access to an occupant premises, thesystem comprising: (a) a phone dialing mechanism adapted to place atelephone call; (b) a notification mechanism responsive to the phonedialing mechanism to cause a notification to be provided from a centraloffice to a telephonic device at the occupant premises, the notificationsignifying that a visitor is present; (c) an automated voice enunciationmechanism adapted to provide an enunciated voice message to the visitorindicative of progress of the telephone call and corresponding to atleast one of busy signal, dial tone, and an answered call; (d) acommunications path establishment mechanism operative, when thetelephone call is answered, so as to provide a communications pathbetween the visitor and the occupant premises, thereby enabling anoccupant to determine whether or not to grant access to the visitor; and(e) an access control mechanism at the occupant premises adapted to beactivated if access is to be provided to the visitor.
 25. The system ofclaim 24 wherein the communications path is provided using a slow scanvideo link.
 26. The system of claim 25 wherein the slow scan video linkis implemented using modems.
 27. A system for providing selective accessto an occupant premises, including: (a) a first translation mechanismfor translating telephone signalling tones into voice; (b) a secondtranslation mechanism for detecting a call status and translating thecall status into one or more enunciated voice prompts using storeddigital voice representations; (c) an association mechanism forassociating an occupant premises identifier with an occupant premisestelephone number and a door answering device telephone number, so as toenable signalling of an occupant premises by placing a telephone callover the public switched telephone network to the door answering devicetelephone number.